It has been an enigma amongst golfers both amateurs and professionals, as to why some putters work better than others. This is not always a question of skill in use, although this is a factor, but by and large it has been the experience of all types of golfers that some putters give a better performance in anyone's hands, than others.
Recently, the capabilities and performance of existing putters have been the subject of investigation and serious study. So far as is known, no existing putter has involved a design which featured a structure to function in accordance with the principles of the mechanics of motion as opposed to static mechanics. In particular, none has been structured to minimize the onset of twisting (viz., angular acceleration) of the putter during the period of impact, while maintaining a high and stable moment of inertia.
A moment's observation shows that the act of putting is that of striking a golf ball on a putting green with a putter in a predetermined direction and at a predetermined distance, with sufficient force to have the ball travel to and drop into the hole. If the golfer incorrectly determines the direction, which is the aim, and/or incorrectly determines the force to be applied to the ball, the putt will be a failure in that the ball will not fall into the hole. If the determination of direction and force (and the execution) are correct, the putt should be a success. Both alignment and force are the conscious acts of the golfer. Alignment has been studied for the purpose of helping the golfer make a correct determination of the direction or aim. Great help has been given to the golfer by putters supplied in recent years under the "ZEBRA" trademark, (see U.S. Pat. No. 3,954,265), with multiple equal and alternate stripes over a substantial area of the top surface of the head. This has greatly aided in making correct aim possible with a minimum of conscious determination by the golfer.
The stripes so provided have been an aid in striking the ball on the correct alignment in the so-called "sweet spot". This point has traditionally been considered the center of the putter's striking face without understanding or even agreement as to the reasons for this, or consideration and incorporation of the principles in the design of a putter which would make these results scientifically true. The problem of determining the "sweet spot" has been a fuzzy one over the years. However, the most important feature of a putter is the way in which it reacts in making a putt. This involves the mechanics of motion, and so far as is known, no putter has been designed with respect to the mechanics of motion.
This prompted recent studies which have established that if a ball is struck with the correct force (which is the force applied at the moment of impact and which equals the mass of the golfer-putter unit multiplied by the acceleration of the golfer-putter unit), and this force is correctly applied at the center of the striking face, then the golf ball will be propelled along a correct line toward the hole if and only if the center of effective mass is at or closely adjacent to the center of the striking face. In this study it was also discovered that if the mass of the putter is increased, the acceleration of the golfer-putter unit is less to accomplish the same result under the same circumstances. This of course must be within the limits of an acceptable club head.
Assume the dynamic condition of a putting stroke wherein a putter is advancing toward the ball in the proper direction with its face normal to that direction. If the impact is in every way perfect, the club will continue in the same direction with its face normal to the direction of the putting stroke. In such case, the design of the putter is essentially irrelevant. Of course, such condition almost never occurs due to normal golfer-putter irregularities which affect the putting stroke. Accordingly, immediately after impact, the face is no longer normal to the initial direction of the putting stroke--indicating that something happened during impact. What happened is that the putter face developed angular velocity in addition to its initial linear velocity so that the face is "twisting". The initiation of this angular velocity is angular acceleration. That is to say, before the impact, the angular velocity of the culb face was zero whereas, after impact, the angular velocity has become something greater than zero. This change of state is "angular acceleration" and it occurs during the period of impact. It is the angular acceleration during impact that sends the ball of line and short of its intended distance. After the impact period, there remains angular velocity, but not angular acceleration. Therefore, it is only angular acceleration and the short period of impact that are of importance.
In the light of the foregoing considerations, it became clear that a putter which would minimize angular acceleration (at impact) would be highly desirable. Therefore, attention was given to the relevant equation, in physics, as follows: EQU .alpha.=T/I
Where
.alpha.=angular acceleration
T=torque
I=moment of inertia
From the foregoing, it becomes apparent that to minimize angular acceleration, the putter construction should be such as to both minimize torque and maximize moment of inertia at the moment of impact. It is also essential to define the precise structure for which the torque is to be minimized and the moment of inertia is to be maximized. Specifically, some parts of the golfer-putter unit are relevent and some are not. To differentiate between the relevant and nonrelevant components, it is necessary to understand precisely what happens at impact. In this regard, the putter-ball impact lasts over a short period of time; after the ball leaves contact with the face, subsequent happenings no longer affect the behavior of the ball. The period of contact is therefore all-important. During contact, shock waves reverberate inside the putter head to effect its (and the ball's) behavior. Moreover, shock waves reach up the shaft. The mass of that portion of the shaft that "feels" the shock wave before the ball leaves the face is the reactive or "effective" component that affects the ball's behavior. The rest of the shaft has no effect on the ball. By the time the golfer feels the impact, the ball has left the club face so that the mass of the golfer has no effect on the putt.
The center of effective mass is that point separating the effective mass into two parts which have equal moments of inertia. The center of effective mass is the "sweet spot", and at no other point of contact will the ball and head not deflect.
Thus, three effective masses must be considered and properly defined. First, the entire effective mass, that is, the sum total of all masses that "feel" the shock of impact before the ball leaves the face. Second and third are the "toe side" and "heel side" portions of the effective mass, each of which has the same moment of inertia as the other.
It has been further observed in our studies, that if the impact occurs elsewhere than at the "sweet spot" of the putter, as correctly defined above, the ball will be propelled incorrectly and will have a force vector which will cause the ball to vear to the left or to the right, and therefore fail as a putt. As indicated above (and presently understood) this is because of the angular acceleration developed in the club face during the period of impact. Of course, the golfer is not aware of what causes his mis-putt and probably is not interested in the scientific explanation. However, one involved in putter design can (and should) provide an implement designed to improve the golfer's putt. Also one can (and should) explain the proper use of the implement, if not its scientific design parameters.